/Engine/Source/Runtime/Engine/Classes/Engine/Texture.h
Retrieve a copy of the data for a particular mip. Prefer GetMipImage.
bool GetMipData ( TArray64< uint8 > & OutMipData, int32 BlockIndex, int32 LayerIndex, int32 MipIndex, class [IImageWrapperModule](API\Runtime\ImageWrapper\IImageWrapperModule) * ImageWrapperModule )